Common Fax Issues

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Written by Kanasu Nagathihalli
Created 2021-05-07

The table below outlines error messages, likely causes and potential workarounds to troubleshoot common fax errors.

Error Description Likely Cause Workaround
Connection failed There was no receiver on the other end of the call to connect to. The destination is not configured to receive transactions. Retry, then contact the number to confirm compatibility and connectivity.
Document generation error There was an error while generating the document. This could be because the file was deleted before it was sent. Internal Service Error Retry, if the issue persists, contact SIPSTACK support.
Failed to train with any of the compatible modems A remote fax machine was deleted but the sending and receiving modems could not establish communication. Connectivity Issues Retry, if the issue persists, contact SIPSTACK support.
Fax transmission not established This could be because either no fax machine was detected at the receiving end or there was a lack of call clarity. Connectivity issues, Carrier issues, T.38 Incompatibility issue Retry, then determine whether remote side was configured for T.38.
Long entry lost The call started but the log entry for the call was lost or incomplete. In practice, this is rate, and may indicate a system-wide problem. Internal Service Error Retry, if the issue persists, contact SIPSTACK support.
No response after sending a page The remote fax machine did not acknowledge that it received a page of the fax. Depending on the remote machine's behavior, it may still have printed the page and any preceding pages. Connectivity issues Retry, then contact destination to ensure delivery.
Received no response to DCS or TCF The bulk fax service could not successfully determine the remote machine's fax capabilities. T.38 Incompatibility issue Determine whether remote side was configured for T.38.
The call dropped prematurely The call dropped due to a non-fax transmission error. It is likely that the receiver hung up. Inbound: The destination is a voice number or is not set up to receive faxes. Outbound: The destination is a voice number, or the destination rings for so long that the transmission times out before the handshake can be established. Retry
The HDLC carrier did not stop in a timely manner The fax service initiated a fax transmission with the receiver, but there was a synchronization (timing) error that could not be resolved. Likely low-quality routes. Retry, if network conditions persist, contact SIPSTACK support so we can contact our carrier partner for additional insight.
Timed out waiting for initial communication A call was established with the receiver, and the bulk fax service attempted to establish a fax session. However, there was no fax response from the receiver. This could be due to there being no fax machine on the receiving end or a lack of call clarity. No remote fax machine or poor-quality routes Retry, if network conditions persist, contact SIPSTACK support so we can contact our carrier partner for additional insight.
Unexpected DCN while waiting for DCS or DIS The remote fax machine unexpectedly sent a disconnect message when the fax service asked for the remote fax machine's fax capabilities. T.38 Incompatibility issue Determine whether remote side was configured for T.38 only.
Disconnected after permitted retries The fax service attempted to send the same message multiple times unsuccessfully. this may be due to a call clarity issue. Poor network conditions Retry, if network conditions persist, contact SIPSTACK support so we can contact our carrier partner for additional insight.
Far end cannot receive at the resolution of the image The remote fax machine does not have the capability to support faxes in that resolution. Quality is too high Try lowering quality and resend fax.
Received a DCN from remote after sending a page The remote fax machine responded with a disconnect message after a page was sent successfully. Depending on the remote machine's behavior, it may have still printed the sent page and any preceding pages. Poor network conditions Retry, if network conditions persist, contact SIPSTACK support so we can contact our carrier partner for additional insight.
Unexpected message received The fax service received a message that it did not expect given the current context. Protocol failure Determine whether the expected number of pages matches the number of successfully transmitted pages. Failure may have been in tearing down the call.
Unexpected DCM after EOM or MPS sequence The remote fax machine disconnected unexpectedly after receiving a page of a multi-page fax. Depending on the remote machine's behavior, it may have still printed the sent page and any preceding pages. Poor network conditions Retry, if network conditions persist, contact SIPSTACK support so we can contact our carrier partner for additional insight.
Document loading error The fax service attempted to generate the message to send, but a document was missing. Internal service error Retry, if the issue persists, contact SIPSTACK support.
Invalid ECM response received from receiver The fax service received an invalid error correction message from the remote fax machine. T.38 Incompatibility issue Retry, if failures only occur with one number, there's a chance that the remote fax machine is incompatible with our infrastructure.
Unexpected DCN after RR/RNR sequence The remote fax machine disconnected unexpectedly after indicating that it was not ready to initiate a fax session. Unexpected failure Retry, if failures only occur with one number, there's a chance that the remote fax machine is incompatible with our infrastructure.
Table 1
Notes:
  1. SIPSTACK only supports faxes sent using the T.30 protocol.
  2. SIPSTACK fax only supports the transmission of PDFs to Fax-enabled destinations.

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